Citation: Arsi´ c, D.; Lazi´ c, V.; Nikoli´ c, R.R.; Sczygiol, N.; Krsti´ c, B.; Ivkovi´ c, D.; Hadzima, B.; Pastorek, F.; Ulewicz, R. Weldability Assessment of Various Steels by Hard-Facing. Materials 2022, 15, 3082. https:// doi.org/10.3390/ma15093082 Academic Editor: Marco Corradi Received: 12 March 2022 Accepted: 21 April 2022 Published: 24 April 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Weldability Assessment of Various Steels by Hard-Facing Dušan Arsi´ c 1 , Vuki´ c Lazi´ c 1 , Ružica R. Nikoli´ c 2, * , Norbert Sczygiol 3 , Božidar Krsti´ c 1 , Djordje Ivkovi´ c 1 , Branislav Hadzima 2 , Filip Pastorek 2 and Robert Ulewicz 4 1 Faculty of Engineering, University of Kragujevac, Sestre Janji´ c 6, 34000 Kragujevac, Serbia; dusan.arsic@fink.rs (D.A.); vlazic@kg.ac.rs (V.L.); bkrstic@kg.ac.rs (B.K.); ivkovic99djordje@gmail.com (D.I.) 2 Research Center, University of Žilina, Univerzitna 8215/1, 010 26 Žilina, Slovakia; branislav.hadzima@uniza.sk (B.H.); filip.pastorek@uniza.sk (F.P.) 3 Faculty of Mechanical Engineering and Computer Science, Czestochowa University of Technology, 42201 Czestochowa, Poland; norbert.sczygiol@pcz.pl 4 Department of Production Engineering and Safety, Czestochowa University of Technology, 42201 Czestochowa, Poland; robert.ulewicz@pcz.pl * Correspondence: ruzica.nikolic@uniza.sk Abstract: Two aspects of various steels’ weldability are considered in this article. The theoretical part presents general concepts related to steel’s weldability and the application of the most important methods for its determination. In the experimental section, results of the hard-facing application to several samples are presented, and consist of hardness measurements in the different zones of the welded samples, with the evaluation of those zones’ microstructures. The tested materials included two carbon steels and two alloyed steels, with hard-facing layers deposited by various filler metals. Experimental results were compared to results obtained by calculations; using both, authors were able to conclude which combination of filler metal, welding procedure and, if necessary, heat treatment, would achieve the optimal improvement of weldability in welding/hard-facing of each of the tested base metals. Keywords: weldability; carbon steel; alloyed steel; hardness; microstructure; preheating 1. Introduction Material weldability is an area of material science in which research into the design and execution of the welding and accompanying technologies is very important. During welding, very complex phenomena occur in the material; the knowledge of which is necessary for successfully welding. Owing to existence of numerous welding methods, it is now possible to successfully join various materials into an unbreakable whole. Weldability is a complex property of metals, which has led to the emergence of several different definitions of the term. However, a unique and explicit definition of weldability, which would be extremely important for the practice of this phenomenon, does not exist. The weldability determines the relative capability of a certain material to form joints of the required quality level by the application of the corresponding procedure and technology. During welding, certain materials can possess good weldability, conditional weldability, or poor weldability. The estimation of the weldability of various metals is of a great importance, both during the selection of filler metals (FM) and methods for manufacturing the welded structures, as well as during the selection of filler metals and procedures for reparation of damaged workpieces of various constructions. Estimating weldability based on a single method is not reliable. The contemporary approach to weldability estimation includes the following: the application of the computer methods that are taking the limit conditions into account, tests with simulations of the temperature cycles during the welding/hard- facing, and tests on samples with the real welding parameters. Determination of the chemical composition, hardness, and toughness of the base metal (BM), as well as of the Materials 2022, 15, 3082. https://doi.org/10.3390/ma15093082 https://www.mdpi.com/journal/materials